This application is related to an antenna, and more particularly to an antenna adapted to operate in more than one frequency band.
With the increased use of wireless communication devices, spectrum has become scarce. In many cases, network operators providing services on one particular band have had to provide service on a separate band to accommodate its customers. For example, service in a given region could be provided on a GSM system in a 900 MHz frequency band and on a DCS system at an 1800 MHz frequency band, or even a third system, such as a PCS system in a 1900 frequency band. Similarly, service in another region could include an AMPS system in an 800 MHz frequency band and a PCS system in a 1900 frequency band. Although a single network operator may not provide service in both systems in a given region, a user of a wireless communication device may like the opportunity to roam in the event he is unable to obtain service on one of the systems. Accordingly, wireless communication devices, such as cellular radio telephones, must be able to communicate at both frequencies.
Further, in a device having a retractable whip antenna in the down or retracted position, the whip is still fed by coupling energy into the antenna through the bushing. Accordingly, the antenna must be rematched the down position. A conventional mechanical switch or a pin diode can be used to change the matching circuit between the antenna and the transceiver when in up and down positions. However, there are several disadvantages of using the switch for changing the matching circuit in the up and down positions. Aside from making the circuitry more complicated, switches add additional power loss when transmitting and receiving. More importantly, a mechanical switch is easily broken and a pin diode switch can be easily broken down by static discharge. Accordingly, there is a need for an antenna which can operate on more than one frequency, including such an antenna being retractable and having a novel matching circuit for the up and down positions.